The following is a tabulation of some prior art that presently appears relevant:
U.S. PatentsPat. No.Kind CodeIssue DatePatentee5,829,866ANov. 3, 1998Stegeman7,364,328B2Apr. 29, 2008 Lee et al.7,430,120B2Sep. 30, 2008 Lau7,597,450B2Oct. 6, 2009GarrettU.S. Patent Application PublicationsPublication Number Kind CodePubl. DateApplicantNone found